feat: qbz-1 streaming, gapless prefetch, accurate scrobbling, Range-seek

Port proven playback architecture from qbqt fork:
- Bounded VecDeque buffer with condvar backpressure (4MB cap)
- decrypt_and_extract_frames for clean FLAC frame extraction from ISOBMFF
- Cancel+restart seeking with sub-segment sample skipping
- start_prefetch / QueueNext for gapless transitions with pre-started downloads
- track_transitioned signaling for scrobbler during gapless playback
- Range-request HTTP seeking for non-segmented (MP3) tracks
- OnceLock HTTP client singleton with cancel-aware chunked downloads
- Accumulated listening time scrobbling (prevents false scrobbles from seeking)
- Array-format Last.fm scrobble params (artist[0], track[0], etc.)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -2,6 +2,17 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "aes"
+version = "0.8.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b169f7a6d4742236a0a00c541b845991d0ac43e546831af1249753ab4c3aa3a0"
+dependencies = [
+ "cfg-if",
+ "cipher",
+ "cpufeatures",
+]
+
 [[package]]
 name = "aho-corasick"
 version = "1.1.4"
@@ -93,6 +104,24 @@ version = "2.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "843867be96c8daad0d758b57df9392b6d8d271134fce549de6ce169ff98a92af"
 
+[[package]]
+name = "block-buffer"
+version = "0.10.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3078c7629b62d3f0439517fa394996acacc5cbc91c5a20d8c658e77abd503a71"
+dependencies = [
+ "generic-array",
+]
+
+[[package]]
+name = "block-padding"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a8894febbff9f758034a5b8e12d87918f56dfc64a8e1fe757d65e29041538d93"
+dependencies = [
+ "generic-array",
+]
+
 [[package]]
 name = "bumpalo"
 version = "3.20.2"
@@ -111,6 +140,15 @@ version = "1.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1e748733b7cbc798e1434b6ac524f0c1ff2ab456fe201501e6497c8417a4fc33"
 
+[[package]]
+name = "cbc"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "26b52a9543ae338f279b96b0b9fed9c8093744685043739079ce85cd58f289a6"
+dependencies = [
+ "cipher",
+]
+
 [[package]]
 name = "cc"
 version = "1.2.57"
@@ -150,6 +188,16 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "613afe47fcd5fac7ccf1db93babcb082c5994d996f20b8b159f2ad1658eb5724"
 
+[[package]]
+name = "cipher"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "773f3b9af64447d2ce9850330c473515014aa235e6a783b02db81ff39e4a3dad"
+dependencies = [
+ "crypto-common",
+ "inout",
+]
+
 [[package]]
 name = "clang-sys"
 version = "1.8.1"
@@ -221,12 +269,51 @@ dependencies = [
  "windows",
 ]
 
+[[package]]
+name = "cpufeatures"
+version = "0.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59ed5838eebb26a2bb2e58f6d5b5316989ae9d08bab10e0e6d103e656d1b0280"
+dependencies = [
+ "libc",
+]
+
+[[package]]
+name = "crypto-common"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "78c8292055d1c1df0cce5d180393dc8cce0abec0a7102adb6c7b1eef6016d60a"
+dependencies = [
+ "generic-array",
+ "typenum",
+]
+
+[[package]]
+name = "ctr"
+version = "0.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0369ee1ad671834580515889b80f2ea915f23b8be8d0daa4bbaf2ac5c7590835"
+dependencies = [
+ "cipher",
+]
+
 [[package]]
 name = "dasp_sample"
 version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0c87e182de0887fd5361989c677c4e8f5000cd9491d6d563161a8f3a5519fc7f"
 
+[[package]]
+name = "digest"
+version = "0.10.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ed9a281f7bc9b7576e61468ba615a66a5c8cfdff42420a70aa82701a3b1e292"
+dependencies = [
+ "block-buffer",
+ "crypto-common",
+ "subtle",
+]
+
 [[package]]
 name = "dirs"
 version = "5.0.1"
@@ -372,6 +459,16 @@ dependencies = [
  "slab",
 ]
 
+[[package]]
+name = "generic-array"
+version = "0.14.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85649ca51fd72272d7821adaf274ad91c288277713d9c18820d8499a7ff69e9a"
+dependencies = [
+ "typenum",
+ "version_check",
+]
+
 [[package]]
 name = "getrandom"
 version = "0.2.17"
@@ -411,6 +508,30 @@ version = "0.16.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "841d1cc9bed7f9236f321df977030373f4a4163ae1a7dbfe1a51a2c1a51d9100"
 
+[[package]]
+name = "hex"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
+
+[[package]]
+name = "hkdf"
+version = "0.12.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b5f8eb2ad728638ea2c7d47a21db23b7b58a72ed6a38256b8a1849f15fbbdf7"
+dependencies = [
+ "hmac",
+]
+
+[[package]]
+name = "hmac"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6c49c37c09c17a53d937dfbb742eb3a961d65a994e6bcdcf37e7399d0cc8ab5e"
+dependencies = [
+ "digest",
+]
+
 [[package]]
 name = "http"
 version = "1.4.0"
@@ -623,6 +744,16 @@ dependencies = [
  "hashbrown",
 ]
 
+[[package]]
+name = "inout"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "879f10e63c20629ecabbb64a8010319738c66a5cd0c29b02d63d272b03751d01"
+dependencies = [
+ "block-padding",
+ "generic-array",
+]
+
 [[package]]
 name = "ipnet"
 version = "2.12.0"
@@ -1054,14 +1185,21 @@ dependencies = [
 name = "qobuz-backend"
 version = "0.1.0"
 dependencies = [
+ "aes",
  "anyhow",
+ "base64",
+ "cbc",
  "cpal",
+ "ctr",
  "dirs",
+ "hex",
+ "hkdf",
  "md5",
  "rb",
  "reqwest",
  "serde",
  "serde_json",
+ "sha2",
  "symphonia",
  "thiserror 2.0.18",
  "tokio",
@@ -1410,6 +1548,17 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "sha2"
+version = "0.10.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a7507d819769d01a365ab707794a4084392c824f54a7a6a7862f8c3d0892b283"
+dependencies = [
+ "cfg-if",
+ "cpufeatures",
+ "digest",
+]
+
 [[package]]
 name = "shlex"
 version = "1.3.0"
@@ -1943,6 +2092,12 @@ version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e421abadd41a4225275504ea4d6566923418b7f05506fbc9c0fe86ba7396114b"
 
+[[package]]
+name = "typenum"
+version = "1.19.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "562d481066bde0658276a35467c4af00bdc6ee726305698a55b86e61d7ad82bb"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.24"
@@ -1973,6 +2128,12 @@ version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b6c140620e7ffbb22c2dee59cafe6084a59b5ffc27a8859a5f0d494b5d52b6be"
 
+[[package]]
+name = "version_check"
+version = "0.9.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
+
 [[package]]
 name = "walkdir"
 version = "2.5.0"

rust/Cargo.toml

@@ -28,6 +28,15 @@ md5 = "0.7"
 dirs = "5"
 toml = "0.8"
 
+# Crypto — qbz-1 key derivation + segment decryption
+aes   = "0.8"
+cbc   = { version = "0.1", features = ["alloc"] }
+ctr   = "0.9"
+hkdf  = "0.12"
+sha2  = "0.10"
+hex   = "0.4"
+base64 = "0.22"
+
 [profile.release]
 lto = "thin"
 opt-level = 3

rust/include/qobuz_backend.h

@@ -75,17 +75,13 @@ uint64_t qobuz_backend_get_duration(const QobuzBackendOpaque *backend);
 uint8_t  qobuz_backend_get_volume(const QobuzBackendOpaque *backend);
 int      qobuz_backend_get_state(const QobuzBackendOpaque *backend);
 int      qobuz_backend_take_track_finished(QobuzBackendOpaque *backend);
+int      qobuz_backend_take_track_transitioned(QobuzBackendOpaque *backend);
 
 // ReplayGain / Gapless
 void qobuz_backend_set_replaygain(QobuzBackendOpaque *backend, bool enabled);
 void qobuz_backend_set_gapless(QobuzBackendOpaque *backend, bool enabled);
 void qobuz_backend_prefetch_track(QobuzBackendOpaque *backend, int64_t track_id, int32_t format_id);
 
-// Visualizer PCM access
-uint32_t qobuz_backend_viz_read(QobuzBackendOpaque *backend, float *buf, uint32_t max_samples);
-uint32_t qobuz_backend_viz_sample_rate(const QobuzBackendOpaque *backend);
-uint32_t qobuz_backend_viz_channels(const QobuzBackendOpaque *backend);
-
 // Artist releases (auto-paginates to fetch all)
 void qobuz_backend_get_artist_releases(QobuzBackendOpaque *backend, int64_t artist_id, const char *release_type, uint32_t limit, uint32_t offset);
 

rust/src/api/client.rs

@@ -1,6 +1,10 @@
 use anyhow::{bail, Result};
+use base64::{engine::general_purpose::URL_SAFE_NO_PAD, Engine};
+use cbc::cipher::{block_padding::NoPadding, BlockDecryptMut, KeyIvInit};
+use hkdf::Hkdf;
 use reqwest::Client;
 use serde_json::Value;
+use sha2::Sha256;
 use std::time::{SystemTime, UNIX_EPOCH};
 
 use super::models::*;
@@ -15,10 +19,66 @@ pub const DEFAULT_APP_SECRET: &str = "e79f8b9be485692b0e5f9dd895826368";
 pub struct QobuzClient {
     http: Client,
     pub auth_token: Option<String>,
+    /// Playback session ID from POST /session/start — sent as X-Session-Id for /file/url.
+    session_id: Option<String>,
+    session_expires_at: Option<u64>,
+    /// `infos` field from the session/start response — used to derive the KEK for track key unwrapping.
+    session_infos: Option<String>,
     app_id: String,
     app_secret: String,
 }
 
+// ── qbz-1 key derivation helpers ─────────────────────────────────────────────
+
+type Aes128CbcDec = cbc::Decryptor<aes::Aes128>;
+
+/// Decode a base64url string (with or without padding).
+fn b64url_decode(s: &str) -> Result<Vec<u8>> {
+    Ok(URL_SAFE_NO_PAD.decode(s.trim_end_matches('='))?)
+}
+
+/// Full qbz-1 key derivation:
+///   Phase 1: HKDF-SHA256(ikm=hex(app_secret), salt=b64url(infos[0]), info=b64url(infos[1])) → 16-byte KEK
+///   Phase 2: AES-128-CBC/NoPadding(key=KEK, iv=b64url(key_field[2])).decrypt(b64url(key_field[1]))[..16]
+fn derive_track_key(session_infos: &str, app_secret_hex: &str, key_field: &str) -> Result<[u8; 16]> {
+    // Phase 1: HKDF
+    let infos_parts: Vec<&str> = session_infos.splitn(2, '.').collect();
+    if infos_parts.len() != 2 {
+        bail!("session_infos must be '<salt_b64>.<info_b64>', got: {session_infos}");
+    }
+    let salt = b64url_decode(infos_parts[0])?;
+    let info = b64url_decode(infos_parts[1])?;
+    let ikm = hex::decode(app_secret_hex)?;
+
+    let hk = Hkdf::<Sha256>::new(Some(&salt), &ikm);
+    let mut kek = [0u8; 16];
+    hk.expand(&info, &mut kek)
+        .map_err(|e| anyhow::anyhow!("HKDF expand failed: {e:?}"))?;
+
+    // Phase 2: AES-128-CBC/NoPadding
+    let key_parts: Vec<&str> = key_field.splitn(3, '.').collect();
+    if key_parts.len() != 3 || key_parts[0] != "qbz-1" {
+        bail!("unexpected key field format: {key_field}");
+    }
+    let ct = b64url_decode(key_parts[1])?;
+    let iv_bytes = b64url_decode(key_parts[2])?;
+    if ct.len() < 16 || iv_bytes.len() < 16 {
+        bail!("key field ciphertext/iv too short ({} / {} bytes)", ct.len(), iv_bytes.len());
+    }
+
+    let iv: [u8; 16] = iv_bytes[..16].try_into()?;
+    let mut buf = ct;
+    let decrypted = Aes128CbcDec::new(&kek.into(), &iv.into())
+        .decrypt_padded_mut::<NoPadding>(&mut buf)
+        .map_err(|e| anyhow::anyhow!("AES-CBC decrypt failed: {e:?}"))?;
+
+    let mut track_key = [0u8; 16];
+    track_key.copy_from_slice(&decrypted[..16]);
+    Ok(track_key)
+}
+
+// ─────────────────────────────────────────────────────────────────────────────
+
 impl QobuzClient {
     pub fn new() -> Result<Self> {
         Self::new_with_config(None, None)
@@ -44,6 +104,9 @@ impl QobuzClient {
         Ok(Self {
             http,
             auth_token: None,
+            session_id: None,
+            session_expires_at: None,
+            session_infos: None,
             app_id,
             app_secret,
         })
@@ -106,20 +169,16 @@ impl QobuzClient {
         if let Some(token) = &self.auth_token {
             builder = builder.header("Authorization", format!("Bearer {}", token));
         }
+        if let Some(sid) = &self.session_id {
+            builder = builder.header("X-Session-Id", sid.as_str());
+        }
         builder
     }
 
     // --- Auth ---
 
-    pub async fn login(&mut self, email: &str, password: &str) -> Result<OAuthLoginResponse> {
-        match self.oauth2_login(email, password).await {
-            Ok(r) => Ok(r),
-            Err(_) => self.legacy_login(email, password).await,
-        }
-    }
-
     /// NOTE: Qobuz API requires credentials as GET query params — not our choice.
-    async fn oauth2_login(&mut self, email: &str, password: &str) -> Result<OAuthLoginResponse> {
+    pub async fn login(&mut self, email: &str, password: &str) -> Result<OAuthLoginResponse> {
         let ts = Self::ts();
         let mut sign_params: Vec<(&str, String)> = vec![
             ("password", password.to_string()),
@@ -144,44 +203,14 @@ impl QobuzClient {
         let body: Value = resp.json().await?;
         if !status.is_success() {
             let msg = body.get("message").and_then(|m| m.as_str()).unwrap_or("login failed");
-            bail!("oauth2 login failed ({}): {}", status, msg);
+            bail!("login failed ({}): {}", status, msg);
-        }
-
-        self.extract_and_store_token(serde_json::from_value(body)?)
-    }
-
-    async fn legacy_login(&mut self, email: &str, password: &str) -> Result<OAuthLoginResponse> {
-        let ts = Self::ts();
-        let mut sign_params: Vec<(&str, String)> = vec![
-            ("email", email.to_string()),
-            ("password", password.to_string()),
-        ];
-        let sig = self.request_sig("userlogin", &mut sign_params, ts);
-
-        let resp = self
-            .http
-            .get(self.url("user/login"))
-            .query(&[
-                ("app_id", self.app_id.as_str()),
-                ("email", email),
-                ("password", password),
-                ("request_ts", ts.to_string().as_str()),
-                ("request_sig", sig.as_str()),
-            ])
-            .send()
-            .await?;
-
-        let status = resp.status();
-        let body: Value = resp.json().await?;
-        if !status.is_success() {
-            let msg = body.get("message").and_then(|m| m.as_str()).unwrap_or("login failed");
-            bail!("user login failed ({}): {}", status, msg);
         }
 
         self.extract_and_store_token(serde_json::from_value(body)?)
     }
 
     fn extract_and_store_token(&mut self, login: OAuthLoginResponse) -> Result<OAuthLoginResponse> {
+        // auth_token = OAuth2 bearer (preferred) or legacy session token
         if let Some(token) = login
             .oauth2
             .as_ref()
@@ -190,9 +219,57 @@ impl QobuzClient {
         {
             self.auth_token = Some(token);
         }
+        // Reset any cached playback session — it belongs to a different auth context.
+        self.session_id = None;
+        self.session_expires_at = None;
+        self.session_infos = None;
         Ok(login)
     }
 
+    /// Start a playback session via POST /session/start.
+    /// The returned session_id is required as X-Session-Id when calling /file/url.
+    /// Sessions expire; we cache and reuse until 60s before expiry.
+    async fn ensure_session(&mut self) -> Result<()> {
+        let now = Self::ts();
+        if let (Some(_), Some(exp)) = (&self.session_id, self.session_expires_at) {
+            if now + 60 < exp {
+                return Ok(()); // still valid
+            }
+        }
+
+        let ts = Self::ts();
+        let mut sign_params: Vec<(&str, String)> = vec![
+            ("profile", "qbz-1".to_string()),
+        ];
+        let sig = self.request_sig("sessionstart", &mut sign_params, ts);
+
+        let resp = self
+            .http
+            .post(self.url("session/start"))
+            .query(&[
+                ("app_id", self.app_id.as_str()),
+                ("request_ts", ts.to_string().as_str()),
+                ("request_sig", sig.as_str()),
+            ])
+            .header("Authorization", format!("Bearer {}", self.auth_token.as_deref().unwrap_or("")))
+            .form(&[("profile", "qbz-1")])
+            .send()
+            .await?;
+
+        let body = Self::check_response(resp).await?;
+        let session_id = body["session_id"]
+            .as_str()
+            .ok_or_else(|| anyhow::anyhow!("session/start: no session_id in response"))?
+            .to_string();
+        let expires_at = body["expires_at"].as_u64().unwrap_or(now + 3600);
+        let infos = body["infos"].as_str().map(|s| s.to_string());
+        eprintln!("[session] started session_id={}... expires_at={} infos={:?}", &session_id[..session_id.len().min(8)], expires_at, infos);
+        self.session_id = Some(session_id);
+        self.session_expires_at = Some(expires_at);
+        self.session_infos = infos;
+        Ok(())
+    }
+
     // --- User ---
 
     pub async fn get_user(&self) -> Result<UserDto> {
@@ -215,7 +292,9 @@ impl QobuzClient {
         Ok(serde_json::from_value(body)?)
     }
 
-    pub async fn get_track_url(&self, track_id: i64, format: Format) -> Result<TrackFileUrlDto> {
+    pub async fn get_track_url(&mut self, track_id: i64, format: Format) -> Result<TrackFileUrlDto> {
+        self.ensure_session().await?;
+
         let ts = Self::ts();
         let intent = "stream";
         let mut sign_params: Vec<(&str, String)> = vec![
@@ -223,10 +302,10 @@ impl QobuzClient {
             ("intent", intent.to_string()),
             ("track_id", track_id.to_string()),
         ];
-        let sig = self.request_sig("trackgetFileUrl", &mut sign_params, ts);
+        let sig = self.request_sig("fileurl", &mut sign_params, ts);
 
         let resp = self
-            .get_request("track/getFileUrl")
+            .get_request("file/url")
             .query(&[
                 ("track_id", track_id.to_string()),
                 ("format_id", format.id().to_string()),
@@ -238,7 +317,24 @@ impl QobuzClient {
             .await?;
 
         let body = Self::check_response(resp).await?;
-        Ok(serde_json::from_value(body)?)
+        eprintln!("[file/url] response: {}", serde_json::to_string(&body).unwrap_or_default());
+        let mut url_dto: TrackFileUrlDto = serde_json::from_value(body)?;
+
+        // Unwrap the per-track key: decrypt the CBC-wrapped key using HKDF-derived KEK.
+        if let (Some(key_field), Some(infos)) = (url_dto.key.clone(), self.session_infos.as_deref()) {
+            match derive_track_key(infos, &self.app_secret, &key_field) {
+                Ok(track_key) => {
+                    url_dto.key = Some(hex::encode(track_key));
+                    eprintln!("[key] track key unwrapped OK");
+                }
+                Err(e) => {
+                    eprintln!("[key] track key unwrap failed: {e}");
+                    url_dto.key = None; // disable decryption rather than play garbage
+                }
+            }
+        }
+
+        Ok(url_dto)
     }
 
     // --- Album ---
@@ -289,17 +385,48 @@ impl QobuzClient {
     // --- Search ---
 
     pub async fn search(&self, query: &str, offset: u32, limit: u32) -> Result<SearchCatalogDto> {
+        let (tracks, albums, artists) = tokio::try_join!(
+            self.search_tracks(query, offset, limit),
+            self.search_albums(query, offset, limit),
+            self.search_artists(query, offset, limit),
+        )?;
+        Ok(SearchCatalogDto {
+            query: Some(query.to_string()),
+            albums: Some(albums),
+            tracks: Some(tracks),
+            artists: Some(artists),
+            playlists: None,
+        })
+    }
+
+    async fn search_tracks(&self, query: &str, offset: u32, limit: u32) -> Result<SearchResultItems<TrackDto>> {
         let resp = self
-            .get_request("catalog/search")
+            .get_request("track/search")
-            .query(&[
+            .query(&[("query", query), ("offset", &offset.to_string()), ("limit", &limit.to_string())])
-                ("query", query),
-                ("offset", &offset.to_string()),
-                ("limit", &limit.to_string()),
-            ])
             .send()
             .await?;
         let body = Self::check_response(resp).await?;
-        Ok(serde_json::from_value(body)?)
+        Ok(serde_json::from_value(body["tracks"].clone())?)
+    }
+
+    async fn search_albums(&self, query: &str, offset: u32, limit: u32) -> Result<SearchResultItems<AlbumDto>> {
+        let resp = self
+            .get_request("album/search")
+            .query(&[("query", query), ("offset", &offset.to_string()), ("limit", &limit.to_string())])
+            .send()
+            .await?;
+        let body = Self::check_response(resp).await?;
+        Ok(serde_json::from_value(body["albums"].clone())?)
+    }
+
+    async fn search_artists(&self, query: &str, offset: u32, limit: u32) -> Result<SearchResultItems<ArtistDto>> {
+        let resp = self
+            .get_request("artist/search")
+            .query(&[("query", query), ("offset", &offset.to_string()), ("limit", &limit.to_string())])
+            .send()
+            .await?;
+        let body = Self::check_response(resp).await?;
+        Ok(serde_json::from_value(body["artists"].clone())?)
     }
 
     // --- Favorites / Library ---
@@ -329,34 +456,103 @@ impl QobuzClient {
         Ok(serde_json::from_value(body)?)
     }
 
-    pub async fn get_fav_tracks(&self, offset: u32, limit: u32) -> Result<SearchResultItems<TrackDto>> {
+    /// Fetch all favorite IDs (tracks, albums, artists) in one call.
+    async fn get_fav_ids(&self) -> Result<FavIdsDto> {
         let resp = self
-            .get_request("favorite/getUserFavorites")
+            .get_request("favorite/getUserFavoriteIds")
-            .query(&[("type", "tracks"), ("offset", &offset.to_string()), ("limit", &limit.to_string())])
             .send()
             .await?;
         let body = Self::check_response(resp).await?;
-        Ok(serde_json::from_value(body["tracks"].clone())?)
+        Ok(serde_json::from_value(body)?)
+    }
+
+    /// Batch-fetch tracks by ID via POST /track/getList.
+    async fn get_tracks_by_ids(&self, ids: &[i64]) -> Result<Vec<TrackDto>> {
+        if ids.is_empty() {
+            return Ok(vec![]);
+        }
+        let resp = self
+            .post_request("track/getList")
+            .json(&serde_json::json!({ "tracks_id": ids }))
+            .send()
+            .await?;
+        let body = Self::check_response(resp).await?;
+        let items: Vec<TrackDto> = serde_json::from_value(
+            body["tracks"]["items"].clone(),
+        )
+        .unwrap_or_default();
+        Ok(items)
+    }
+
+    pub async fn get_fav_tracks(&self, offset: u32, limit: u32) -> Result<SearchResultItems<TrackDto>> {
+        let ids = self.get_fav_ids().await?;
+        let all_ids = ids.tracks.unwrap_or_default();
+        let total = all_ids.len() as i32;
+        let page: Vec<i64> = all_ids
+            .into_iter()
+            .skip(offset as usize)
+            .take(limit as usize)
+            .collect();
+        let items = self.get_tracks_by_ids(&page).await?;
+        Ok(SearchResultItems {
+            items: Some(items),
+            total: Some(total),
+            offset: Some(offset as i32),
+            limit: Some(limit as i32),
+        })
     }
 
     pub async fn get_fav_albums(&self, offset: u32, limit: u32) -> Result<SearchResultItems<AlbumDto>> {
-        let resp = self
+        let ids = self.get_fav_ids().await?;
-            .get_request("favorite/getUserFavorites")
+        let all_ids = ids.albums.unwrap_or_default();
-            .query(&[("type", "albums"), ("offset", &offset.to_string()), ("limit", &limit.to_string())])
+        let total = all_ids.len() as i32;
-            .send()
+        let page: Vec<&str> = all_ids
-            .await?;
+            .iter()
-        let body = Self::check_response(resp).await?;
+            .skip(offset as usize)
-        Ok(serde_json::from_value(body["albums"].clone())?)
+            .take(limit as usize)
+            .map(|s| s.as_str())
+            .collect();
+        let mut items = Vec::with_capacity(page.len());
+        for album_id in page {
+            match self.get_album(album_id).await {
+                Ok(a) => items.push(a),
+                Err(e) => eprintln!("[fav] failed to fetch album {}: {}", album_id, e),
+            }
+        }
+        Ok(SearchResultItems {
+            items: Some(items),
+            total: Some(total),
+            offset: Some(offset as i32),
+            limit: Some(limit as i32),
+        })
     }
 
     pub async fn get_fav_artists(&self, offset: u32, limit: u32) -> Result<SearchResultItems<FavArtistDto>> {
-        let resp = self
+        let ids = self.get_fav_ids().await?;
-            .get_request("favorite/getUserFavorites")
+        let all_ids = ids.artists.unwrap_or_default();
-            .query(&[("type", "artists"), ("offset", &offset.to_string()), ("limit", &limit.to_string())])
+        let total = all_ids.len() as i32;
-            .send()
+        let page: Vec<i64> = all_ids
-            .await?;
+            .into_iter()
-        let body = Self::check_response(resp).await?;
+            .skip(offset as usize)
-        Ok(serde_json::from_value(body["artists"].clone())?)
+            .take(limit as usize)
+            .collect();
+        let mut items = Vec::with_capacity(page.len());
+        for artist_id in page {
+            match self.get_artist_page(artist_id).await {
+                Ok(v) => {
+                    if let Ok(a) = serde_json::from_value::<FavArtistDto>(v) {
+                        items.push(a);
+                    }
+                }
+                Err(e) => eprintln!("[fav] failed to fetch artist {}: {}", artist_id, e),
+            }
+        }
+        Ok(SearchResultItems {
+            items: Some(items),
+            total: Some(total),
+            offset: Some(offset as i32),
+            limit: Some(limit as i32),
+        })
     }
 
     // --- Playlist management ---

rust/src/api/models.rs

@@ -74,12 +74,16 @@ pub struct AudioInfoDto {
 #[derive(Debug, Deserialize, Clone, Serialize)]
 pub struct TrackFileUrlDto {
     pub track_id: Option<i64>,
-    pub duration: Option<i64>,
+    pub duration: Option<f64>,
     pub url: Option<String>,
+    pub url_template: Option<String>,
+    pub n_segments: Option<u32>,
     pub format_id: Option<i32>,
     pub mime_type: Option<String>,
     pub sampling_rate: Option<f64>,
     pub bit_depth: Option<i32>,
+    /// qbz-1 encryption key: "qbz-1.<base64url_aes_key>.<base64url_iv>"
+    pub key: Option<String>,
 }
 
 // --- Album ---
@@ -219,6 +223,15 @@ pub struct FavArtistDto {
     pub image: Option<ImageDto>,
 }
 
+// --- Favorite IDs ---
+
+#[derive(Debug, Deserialize, Serialize)]
+pub struct FavIdsDto {
+    pub tracks: Option<Vec<i64>>,
+    pub albums: Option<Vec<String>>,
+    pub artists: Option<Vec<i64>>,
+}
+
 // --- Format ---
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]

rust/src/lib.rs

@@ -81,6 +81,9 @@ struct PrefetchedTrack {
     track_id: i64,
     track: api::models::TrackDto,
     url: String,
+    n_segments: u32,
+    encryption_key: Option<String>,
+    prefetch_data: Option<player::decoder::PrefetchData>,
 }
 
 struct BackendInner {
@@ -476,8 +479,9 @@ pub unsafe extern "C" fn qobuz_backend_play_track(
             }
         };
 
-        let (track, url) = if let Some(pf) = cached {
+        // Extract prefetch_data to embed directly into TrackInfo
-            (pf.track, pf.url)
+        let (track, url, n_segments, encryption_key, prefetch_data) = if let Some(pf) = cached {
+            (pf.track, pf.url, pf.n_segments, pf.encryption_key, pf.prefetch_data)
         } else {
             // Fetch track metadata
             let track = match client.lock().await.get_track(track_id).await {
@@ -489,11 +493,24 @@ pub unsafe extern "C" fn qobuz_backend_play_track(
                 Ok(u) => u,
                 Err(e) => { call_cb(cb, ud, EV_TRACK_URL_ERR, &err_json(&e.to_string())); return; }
             };
-            let url = match url_dto.url {
+            let encryption_key = url_dto.key.clone();
-                Some(u) => u,
+            // Prefer segmented url_template (reliable CDN path), fall back to plain url
-                None => { call_cb(cb, ud, EV_TRACK_URL_ERR, &err_json("no stream URL")); return; }
+            eprintln!("[lib] url_dto: url={:?}, url_template={:?}, n_segments={:?}, mime={:?}, key_present={}",
+                url_dto.url.as_deref().map(|u| &u[..u.len().min(60)]),
+                url_dto.url_template.as_deref().map(|u| &u[..u.len().min(60)]),
+                url_dto.n_segments,
+                url_dto.mime_type,
+                encryption_key.is_some());
+            let (url, n_segments) = if let (Some(tmpl), Some(n)) = (url_dto.url_template, url_dto.n_segments) {
+                (tmpl, n)
+            } else if let Some(u) = url_dto.url {
+                (u, 0u32)
+            } else {
+                call_cb(cb, ud, EV_TRACK_URL_ERR, &err_json("no stream URL"));
+                return;
             };
-            (track, url)
+            eprintln!("[lib] resolved: n_segments={n_segments}, url_prefix={}", &url[..url.len().min(80)]);
+            (track, url, n_segments, encryption_key, None)
         };
 
         // 2. Notify track change
@@ -513,7 +530,7 @@ pub unsafe extern "C" fn qobuz_backend_play_track(
         if let Some(dur) = track.duration {
             status.duration_secs.store(dur as u64, std::sync::atomic::Ordering::Relaxed);
         }
-        let _ = cmd_tx.send(player::PlayerCommand::Play(player::TrackInfo { track, url, replaygain_db }));
+        let _ = cmd_tx.send(player::PlayerCommand::Play(player::TrackInfo { track, url, n_segments, encryption_key, replaygain_db, prefetch_data }));
 
         // 5. State notification
         call_cb(cb, ud, EV_STATE_CHANGED, r#"{"state":"playing"}"#);
@@ -582,6 +599,28 @@ pub unsafe extern "C" fn qobuz_backend_take_track_finished(ptr: *mut Backend) ->
     if finished { 1 } else { 0 }
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn qobuz_backend_take_track_transitioned(ptr: *mut Backend) -> c_int {
+    let inner = &(*ptr).0;
+    let transitioned = inner
+        .player
+        .status
+        .track_transitioned
+        .swap(false, std::sync::atomic::Ordering::SeqCst);
+
+    if transitioned {
+        // Emit track changed so the Qt UI and Scrobbler automatically pick up the new song
+        if let Some(track) = inner.player.status.current_track.lock().unwrap().as_ref() {
+            if let Ok(j) = serde_json::to_string(track) {
+                call_cb(inner.cb, inner.ud, EV_TRACK_CHANGED, &j);
+            }
+        }
+        1
+    } else {
+        0
+    }
+}
+
 // ---------- ReplayGain / Gapless ----------
 
 #[no_mangle]
@@ -600,10 +639,11 @@ pub unsafe extern "C" fn qobuz_backend_prefetch_track(
     track_id: i64,
     format_id: i32,
 ) {
-    let inner  = &(*ptr).0;
+    let inner = &(*ptr).0;
     let client = inner.client.clone();
-    let prefetch = inner.prefetch.clone();
     let format = Format::from_id(format_id);
+    let cmd_tx = inner.player.cmd_tx.clone();
+    let rg_enabled = inner.replaygain_enabled.clone();
 
     spawn(inner, async move {
         let track = match client.lock().await.get_track(track_id).await {
@@ -614,11 +654,41 @@ pub unsafe extern "C" fn qobuz_backend_prefetch_track(
             Ok(u) => u,
             Err(_) => return,
         };
-        let url = match url_dto.url {
+        let encryption_key = url_dto.key.clone();
-            Some(u) => u,
+        let (url, n_segments) = if let (Some(tmpl), Some(n)) = (url_dto.url_template, url_dto.n_segments) {
-            None => return,
+            (tmpl, n)
+        } else if let Some(u) = url_dto.url {
+            (u, 0u32)
+        } else {
+            return;
         };
-        *prefetch.lock().await = Some(PrefetchedTrack { track_id, track, url });
+
+        // KICKSTART DOWNLOADING IMMEDIATELY
+        let prefetch_data = if n_segments > 0 {
+            Some(player::decoder::start_prefetch(
+                url.clone(),
+                n_segments,
+                encryption_key.as_deref(),
+                1,
+            ))
+        } else {
+            None
+        };
+
+        let replaygain_db = if rg_enabled.load(std::sync::atomic::Ordering::Relaxed) {
+            track.audio_info.as_ref().and_then(|ai| ai.replaygain_track_gain)
+        } else {
+            None
+        };
+
+        let _ = cmd_tx.send(player::PlayerCommand::QueueNext(player::TrackInfo {
+            track,
+            url,
+            n_segments,
+            encryption_key,
+            replaygain_db,
+            prefetch_data,
+        }));
     });
 }
 
@@ -717,34 +787,6 @@ pub unsafe extern "C" fn qobuz_backend_get_user(ptr: *mut Backend) {
     });
 }
 
-// ---------- Visualizer PCM access ----------
-
-/// Read up to `max_samples` f32 PCM values into `buf`.
-/// Returns the number of samples actually read.
-#[no_mangle]
-pub unsafe extern "C" fn qobuz_backend_viz_read(
-    ptr: *mut Backend,
-    buf: *mut f32,
-    max_samples: u32,
-) -> u32 {
-    let consumer = &(*ptr).0.player.status.viz_consumer;
-    let Ok(mut lock) = consumer.try_lock() else { return 0 };
-    let slice = std::slice::from_raw_parts_mut(buf, max_samples as usize);
-    rb::RbConsumer::read(&mut *lock, slice).unwrap_or(0) as u32
-}
-
-/// Returns current sample rate of the audio stream (0 if idle).
-#[no_mangle]
-pub unsafe extern "C" fn qobuz_backend_viz_sample_rate(ptr: *const Backend) -> u32 {
-    (*ptr).0.player.status.viz_sample_rate.load(std::sync::atomic::Ordering::Relaxed)
-}
-
-/// Returns current channel count (0 if idle).
-#[no_mangle]
-pub unsafe extern "C" fn qobuz_backend_viz_channels(ptr: *const Backend) -> u32 {
-    (*ptr).0.player.status.viz_channels.load(std::sync::atomic::Ordering::Relaxed)
-}
-
 // ---------- Playlist management ----------
 
 pub const EV_PLAYLIST_CREATED: c_int = 20;

rust/src/player/mod.rs

@@ -1,33 +1,33 @@
-mod decoder;
+pub mod decoder;
 pub mod output;
 
-use rb::{SpscRb, RB};
 use std::sync::{
-    atomic::{AtomicBool, AtomicU32, AtomicU64, AtomicU8, Ordering},
+    atomic::{AtomicBool, AtomicU64, AtomicU8, Ordering},
     Arc,
 };
 use std::time::Duration;
 
 use crate::api::TrackDto;
+use decoder::NextAction;
 
-/// Size of the visualizer ring buffer in f32 samples (~180ms at 44.1kHz stereo).
+#[derive(Clone)]
-const VIZ_RING_SIZE: usize = 16 * 1024;
-
-#[derive(Debug, Clone)]
 pub enum PlayerCommand {
     Play(TrackInfo),
+    QueueNext(TrackInfo),
     Pause,
     Resume,
     Stop,
     SetVolume(u8),
 }
 
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub struct TrackInfo {
     pub track: TrackDto,
     pub url: String,
-    /// ReplayGain track gain in dB, if enabled and available.
+    pub n_segments: u32,
+    pub encryption_key: Option<String>,
     pub replaygain_db: Option<f64>,
+    pub prefetch_data: Option<decoder::PrefetchData>,
 }
 
 #[derive(Debug, Clone, PartialEq)]
@@ -45,26 +45,16 @@ pub struct PlayerStatus {
     pub duration_secs: Arc<AtomicU64>,
     pub volume: Arc<AtomicU8>,
     pub current_track: Arc<std::sync::Mutex<Option<TrackDto>>>,
-    /// Set to true by the decode thread when a track finishes naturally.
     pub track_finished: Arc<AtomicBool>,
-    /// Set by the player loop when a seek command arrives; cleared by the decode thread.
+    pub track_transitioned: Arc<AtomicBool>,
     pub seek_requested: Arc<AtomicBool>,
     pub seek_target_secs: Arc<AtomicU64>,
-    /// Linear gain factor to apply (1.0 = unity). Updated each time a new track starts.
     pub replaygain_gain: Arc<std::sync::Mutex<f32>>,
-    /// When false the audio output is torn down after each track, producing a gap.
     pub gapless: Arc<AtomicBool>,
-    /// Visualizer ring buffer (consumer side, read by FFI).
-    pub viz_ring: Arc<SpscRb<f32>>,
-    pub viz_consumer: Arc<std::sync::Mutex<rb::Consumer<f32>>>,
-    pub viz_sample_rate: Arc<AtomicU32>,
-    pub viz_channels: Arc<AtomicU32>,
 }
 
 impl PlayerStatus {
     pub fn new() -> Self {
-        let viz_ring = Arc::new(SpscRb::new(VIZ_RING_SIZE));
-        let viz_consumer = Arc::new(std::sync::Mutex::new(viz_ring.consumer()));
         Self {
             state: Arc::new(std::sync::Mutex::new(PlayerState::Idle)),
             position_secs: Arc::new(AtomicU64::new(0)),
@@ -72,33 +62,26 @@ impl PlayerStatus {
             volume: Arc::new(AtomicU8::new(80)),
             current_track: Arc::new(std::sync::Mutex::new(None)),
             track_finished: Arc::new(AtomicBool::new(false)),
+            track_transitioned: Arc::new(AtomicBool::new(false)),
             seek_requested: Arc::new(AtomicBool::new(false)),
             seek_target_secs: Arc::new(AtomicU64::new(0)),
             replaygain_gain: Arc::new(std::sync::Mutex::new(1.0)),
             gapless: Arc::new(AtomicBool::new(false)),
-            viz_ring,
-            viz_consumer,
-            viz_sample_rate: Arc::new(AtomicU32::new(0)),
-            viz_channels: Arc::new(AtomicU32::new(0)),
         }
     }
 
     pub fn get_state(&self) -> PlayerState {
         self.state.lock().unwrap().clone()
     }
-
     pub fn get_position(&self) -> u64 {
         self.position_secs.load(Ordering::Relaxed)
     }
-
     pub fn get_duration(&self) -> u64 {
         self.duration_secs.load(Ordering::Relaxed)
     }
-
     pub fn get_volume(&self) -> u8 {
         self.volume.load(Ordering::Relaxed)
     }
-
 }
 
 pub struct Player {
@@ -122,51 +105,45 @@ impl Player {
     pub fn send(&self, cmd: PlayerCommand) {
         self.cmd_tx.send(cmd).ok();
     }
-
     pub fn pause(&self) {
         self.send(PlayerCommand::Pause);
     }
-
     pub fn resume(&self) {
         self.send(PlayerCommand::Resume);
     }
-
     pub fn stop(&self) {
         self.send(PlayerCommand::Stop);
     }
-
     pub fn set_volume(&self, vol: u8) {
         self.status.volume.store(vol, Ordering::Relaxed);
         self.send(PlayerCommand::SetVolume(vol));
     }
-
     pub fn seek(&self, secs: u64) {
         self.status.seek_target_secs.store(secs, Ordering::Relaxed);
         self.status.seek_requested.store(true, Ordering::SeqCst);
     }
 }
 
-/// The player loop runs on a single dedicated OS thread.
-/// It owns the `AudioOutput` locally so there are no Send constraints.
-/// Decoding is performed inline; the command channel is polled via try_recv
-/// inside the decode loop to handle Pause/Resume/Seek/Stop/Play without
-/// tearng down and re-opening the audio device between tracks.
 fn player_loop(rx: std::sync::mpsc::Receiver<PlayerCommand>, status: PlayerStatus) {
     use std::sync::mpsc::RecvTimeoutError;
 
     let mut audio_output: Option<output::AudioOutput> = None;
     let paused = Arc::new(AtomicBool::new(false));
-    // pending_info holds a Play command that interrupted an ongoing decode
+    let mut pending_action: Option<NextAction> = None;
-    let mut pending_info: Option<TrackInfo> = None;
 
     'outer: loop {
-        // Wait for a Play command (or use one that was interrupted)
+        let info = if let Some(action) = pending_action.take() {
-        let info = if let Some(p) = pending_info.take() {
+            match action {
-            p
+                NextAction::Play(info) | NextAction::Transition(info) => info,
+            }
         } else {
             loop {
                 match rx.recv_timeout(Duration::from_millis(100)) {
                     Ok(PlayerCommand::Play(info)) => break info,
+                    Ok(PlayerCommand::QueueNext(info)) => {
+                        // If completely idle and get QueueNext, treat as Play
+                        break info;
+                    }
                     Ok(PlayerCommand::Stop) => {
                         audio_output = None;
                         paused.store(false, Ordering::SeqCst);
@@ -178,15 +155,15 @@ fn player_loop(rx: std::sync::mpsc::Receiver<PlayerCommand>, status: PlayerStatu
                     Ok(PlayerCommand::SetVolume(v)) => {
                         status.volume.store(v, Ordering::Relaxed);
                     }
-                    Ok(_) => {} // Pause/Resume ignored when idle
+                    Ok(_) => {}
                     Err(RecvTimeoutError::Timeout) => {}
                     Err(RecvTimeoutError::Disconnected) => break 'outer,
                 }
             }
         };
 
-        // Compute ReplayGain factor
+        let rg_factor = info
-        let rg_factor = info.replaygain_db
+            .replaygain_db
             .map(|db| 10f32.powf(db as f32 / 20.0))
             .unwrap_or(1.0);
         *status.replaygain_gain.lock().unwrap() = rg_factor;
@@ -199,13 +176,15 @@ fn player_loop(rx: std::sync::mpsc::Receiver<PlayerCommand>, status: PlayerStatu
         status.position_secs.store(0, Ordering::Relaxed);
         paused.store(false, Ordering::SeqCst);
 
-        match decoder::play_track_inline(&info.url, &status, &paused, &mut audio_output, &rx) {
+        match decoder::play_track_inline(info, &status, &paused, &mut audio_output, &rx) {
-            Ok(Some(next_info)) => {
+            Ok(Some(NextAction::Play(next_track))) => {
-                // Interrupted by a new Play — loop immediately with reused audio output
+                pending_action = Some(NextAction::Play(next_track));
-                pending_info = Some(next_info);
+            }
+            Ok(Some(NextAction::Transition(next_track))) => {
+                pending_action = Some(NextAction::Play(next_track));
+                status.track_transitioned.store(true, Ordering::SeqCst);
             }
             Ok(None) => {
-                // Track finished naturally — tear down audio output if gapless is off
                 if !status.gapless.load(Ordering::Relaxed) {
                     audio_output = None;
                 }
@@ -215,8 +194,6 @@ fn player_loop(rx: std::sync::mpsc::Receiver<PlayerCommand>, status: PlayerStatu
             Err(e) => {
                 eprintln!("playback error: {e}");
                 *status.state.lock().unwrap() = PlayerState::Error(e.to_string());
-                // Signal track end so the queue advances to the next track
-                // instead of stalling on an unplayable track.
                 status.track_finished.store(true, Ordering::SeqCst);
             }
         }

rust/src/player/output.rs

@@ -14,7 +14,6 @@ const RING_BUFFER_SIZE: usize = 32 * 1024;
 
 pub struct AudioOutput {
     ring_buf_producer: rb::Producer<f32>,
-    viz_producer: Option<rb::Producer<f32>>,
     _stream: cpal::Stream,
     pub sample_rate: u32,
     pub channels: usize,
@@ -52,17 +51,12 @@ impl AudioOutput {
 
         Ok(Self {
             ring_buf_producer: producer,
-            viz_producer: None,
             _stream: stream,
             sample_rate,
             channels,
         })
     }
 
-    pub fn set_viz_producer(&mut self, producer: rb::Producer<f32>) {
-        self.viz_producer = Some(producer);
-    }
-
     pub fn write(
         &mut self,
         decoded: AudioBufferRef<'_>,
@@ -75,13 +69,13 @@ impl AudioOutput {
         );
         sample_buf.copy_interleaved_ref(decoded);
         let samples: Vec<f32> = sample_buf.samples().iter().map(|s| s * volume).collect();
+        self.write_samples(&samples, stop)
+    }
 
-        // Best-effort copy for visualizer (non-blocking, ok to drop samples)
+    /// Write pre-converted interleaved f32 samples directly to the ring buffer.
-        if let Some(ref mut viz) = self.viz_producer {
+    /// Returns early (without error) if `stop` is set.
-            let _ = viz.write(&samples);
+    pub fn write_samples(&mut self, samples: &[f32], stop: &Arc<AtomicBool>) -> Result<()> {
-        }
+        let mut remaining = samples;
-
-        let mut remaining = &samples[..];
         while !remaining.is_empty() {
             if stop.load(Ordering::SeqCst) {
                 return Ok(());

src/backend/qobuzbackend.cpp

@@ -209,21 +209,6 @@ quint64 QobuzBackend::duration() const { return qobuz_backend_get_duration(m_bac
 int     QobuzBackend::volume()   const { return qobuz_backend_get_volume(m_backend); }
 int     QobuzBackend::state()    const { return qobuz_backend_get_state(m_backend); }
 
-quint32 QobuzBackend::vizRead(float *buf, quint32 maxSamples)
-{
-    return qobuz_backend_viz_read(m_backend, buf, maxSamples);
-}
-
-quint32 QobuzBackend::vizSampleRate() const
-{
-    return qobuz_backend_viz_sample_rate(m_backend);
-}
-
-quint32 QobuzBackend::vizChannels() const
-{
-    return qobuz_backend_viz_channels(m_backend);
-}
-
 // ---- private slots ----
 
 void QobuzBackend::onPositionTick()
@@ -232,6 +217,9 @@ void QobuzBackend::onPositionTick()
 
     if (qobuz_backend_take_track_finished(m_backend))
         emit trackFinished();
+
+    if (qobuz_backend_take_track_transitioned(m_backend))
+        emit trackTransitioned();
 }
 
 void QobuzBackend::onEvent(int eventType, const QString &json)

src/backend/qobuzbackend.hpp

@@ -73,11 +73,6 @@ public:
     /// 1 = playing, 2 = paused, 0 = idle
     int     state() const;
 
-    // --- visualizer PCM ---
-    quint32 vizRead(float *buf, quint32 maxSamples);
-    quint32 vizSampleRate() const;
-    quint32 vizChannels() const;
-
 signals:
     // auth
     void loginSuccess(const QString &token, const QJsonObject &user);
@@ -106,6 +101,7 @@ signals:
     void stateChanged(const QString &state);
     void positionChanged(quint64 position, quint64 duration);
     void trackFinished();
+    void trackTransitioned();
 
     // errors
     void error(const QString &message);

src/list/tracks.cpp

@@ -189,7 +189,7 @@ void Tracks::onContextMenu(const QPoint &pos)
         menu.addSeparator();
         auto *openAlbum = menu.addAction(
             QIcon(":/res/icons/view-media-album-cover.svg"),
-            tr("Open album: %1").arg(m_model->trackAt(index.row()).album));
+            tr("Open album: %1").arg(QString(m_model->trackAt(index.row()).album).replace(QLatin1Char('&'), QStringLiteral("&&"))));
         connect(openAlbum, &QAction::triggered, this, [this, albumId] {
             m_backend->getAlbum(albumId);
         });
@@ -202,7 +202,7 @@ void Tracks::onContextMenu(const QPoint &pos)
         const QString artistName = trackJson["performer"].toObject()["name"].toString();
         auto *openArtist = menu.addAction(
             QIcon(":/res/icons/view-media-artist.svg"),
-            tr("Open artist: %1").arg(artistName));
+            tr("Open artist: %1").arg(QString(artistName).replace(QLatin1Char('&'), QStringLiteral("&&"))));
         connect(openArtist, &QAction::triggered, this, [this, artistId] {
             m_backend->getArtist(artistId);
         });
@@ -216,7 +216,7 @@ void Tracks::onContextMenu(const QPoint &pos)
         for (const auto &pl : m_userPlaylists) {
             const qint64  plId   = pl.first;
             const QString plName = pl.second;
-            auto *act = addToPlMenu->addAction(plName);
+            auto *act = addToPlMenu->addAction(QString(plName).replace(QLatin1Char('&'), QStringLiteral("&&")));
             connect(act, &QAction::triggered, this, [this, id, plId] {
                 emit addToPlaylistRequested(id, plId);
             });

src/mainwindow.cpp

@@ -40,8 +40,7 @@ MainWindow::MainWindow(QobuzBackend *backend, QWidget *parent)
     m_libraryDock->setObjectName(QStringLiteral("libraryDock"));
     m_libraryDock->setFeatures(QDockWidget::DockWidgetMovable);
     m_libraryDock->setWidget(m_library);
-    m_libraryDock->setMinimumWidth(180);
+    m_libraryDock->setMinimumWidth(150);
-    m_library->setFixedWidth(220);
     addDockWidget(Qt::LeftDockWidgetArea, m_libraryDock);
 
     // ---- Now-playing context dock (left, below library) ----
@@ -70,6 +69,10 @@ MainWindow::MainWindow(QobuzBackend *backend, QWidget *parent)
     connect(m_backend, &QobuzBackend::trackFinished,
             m_scrobbler, &LastFmScrobbler::onTrackFinished);
 
+    // Scrobble the finished track during a gapless transition
+    connect(m_backend, &QobuzBackend::trackTransitioned,
+            m_scrobbler, &LastFmScrobbler::onTrackFinished);
+
     // ---- Backend signals ----
     connect(m_backend, &QobuzBackend::loginSuccess,   this, &MainWindow::onLoginSuccess);
     connect(m_backend, &QobuzBackend::loginError,     this, &MainWindow::onLoginError);

src/scrobbler/lastfm.hpp

@@ -78,9 +78,11 @@ public slots:
             m_artist = track["album"].toObject()["artist"].toObject()["name"].toString();
         m_album    = track["album"].toObject()["title"].toString();
         m_duration = static_cast<qint64>(track["duration"].toDouble());
-        m_startTime   = QDateTime::currentSecsSinceEpoch();
+        m_startTime       = QDateTime::currentSecsSinceEpoch();
-        m_playedSecs  = 0;
+        m_playedSecs      = 0;
-        m_scrobbled   = false;
+        m_lastPosition    = 0;
+        m_accumulatedSecs = 0;
+        m_scrobbled       = false;
 
         if (!isEnabled() || m_title.isEmpty() || m_duration < 30) return;
         updateNowPlaying();
@@ -88,18 +90,29 @@ public slots:
 
     void onPositionChanged(quint64 positionSecs, quint64 /*duration*/)
     {
+        // Accumulate actual listening time to prevent false scrobbles from seeking
+        if (positionSecs > m_lastPosition && (positionSecs - m_lastPosition) <= 2) {
+            m_accumulatedSecs += (positionSecs - m_lastPosition);
+        }
+        m_lastPosition = positionSecs;
         m_playedSecs = positionSecs;
+
         if (!isEnabled() || m_scrobbled || m_title.isEmpty() || m_duration < 30) return;
+
         // Scrobble after 50% or 240 seconds played, whichever comes first, min 30 seconds.
         const quint64 threshold = static_cast<quint64>(qMin((qint64)240, m_duration / 2));
-        if (positionSecs >= 30 && positionSecs >= threshold)
+        if (m_accumulatedSecs >= 30 && m_accumulatedSecs >= threshold)
             scrobble();
     }
 
     void onTrackFinished()
     {
         if (!isEnabled() || m_scrobbled || m_title.isEmpty() || m_duration < 30) return;
-        if (m_playedSecs >= 30) scrobble();
+
+        const quint64 threshold = static_cast<quint64>(qMin((qint64)240, m_duration / 2));
+        if (m_accumulatedSecs >= 30 && m_accumulatedSecs >= threshold) {
+            scrobble();
+        }
     }
 
 private:
@@ -108,10 +121,12 @@ private:
     QString m_title;
     QString m_artist;
     QString m_album;
-    qint64  m_duration   = 0;
+    qint64  m_duration        = 0;
-    qint64  m_startTime  = 0;
+    qint64  m_startTime       = 0;
-    quint64 m_playedSecs = 0;
+    quint64 m_playedSecs      = 0;
-    bool    m_scrobbled  = false;
+    quint64 m_lastPosition    = 0;
+    quint64 m_accumulatedSecs = 0;
+    bool    m_scrobbled       = false;
 
     void updateNowPlaying()
     {
@@ -134,16 +149,18 @@ private:
     {
         m_scrobbled = true;
         QMap<QString,QString> params;
-        params["method"]    = QStringLiteral("track.scrobble");
+        params["method"]       = QStringLiteral("track.scrobble");
-        params["api_key"]   = AppSettings::instance().lastFmApiKey();
+        params["api_key"]      = AppSettings::instance().lastFmApiKey();
-        params["sk"]        = AppSettings::instance().lastFmSessionKey();
+        params["sk"]           = AppSettings::instance().lastFmSessionKey();
-        params["artist"]    = m_artist;
+
-        params["track"]     = m_title;
+        params["artist[0]"]    = m_artist;
-        params["album"]     = m_album;
+        params["track[0]"]     = m_title;
-        params["timestamp"] = QString::number(m_startTime);
+        params["album[0]"]     = m_album;
-        params["duration"]  = QString::number(m_duration);
+        params["timestamp[0]"] = QString::number(m_startTime);
-        params["api_sig"]   = buildSig(params, AppSettings::instance().lastFmApiSecret());
+        params["duration[0]"]  = QString::number(m_duration);
-        params["format"]    = QStringLiteral("json");
+
+        params["api_sig"]      = buildSig(params, AppSettings::instance().lastFmApiSecret());
+        params["format"]       = QStringLiteral("json");
 
         auto *reply = m_nam->post(apiRequest(), encodeBody(params));
         connect(reply, &QNetworkReply::finished, reply, &QNetworkReply::deleteLater);

src/view/maintoolbar.cpp

@@ -96,9 +96,11 @@ MainToolBar::MainToolBar(QobuzBackend *backend, PlayQueue *queue, QWidget *paren
 
     // ---- Volume ----
     m_volume = new VolumeButton(this);
-    m_volume->setValue(AppSettings::instance().volume());
     addWidget(m_volume);
     connect(m_volume, &VolumeButton::volumeChanged, this, &MainToolBar::onVolumeChanged);
+    // Set volume after connecting so the backend receives the initial value
+    m_volume->setValue(AppSettings::instance().volume());
+    m_backend->setVolume(AppSettings::instance().volume());
 
     // ---- Queue toggle ----
     m_queueBtn = addAction(Icon::queue(), tr("Queue"));

src/view/sidepanel/view.cpp

@@ -186,13 +186,13 @@ void SearchTab::onTrackContextMenu(const QPoint &pos)
 
     menu.addSeparator();
     if (!albumId.isEmpty()) {
-        auto *openAlbum = menu.addAction(tr("Go to album: %1").arg(albumTitle));
+        auto *openAlbum = menu.addAction(tr("Go to album: %1").arg(QString(albumTitle).replace(QLatin1Char('&'), QStringLiteral("&&"))));
         connect(openAlbum, &QAction::triggered, this, [this, albumId] {
             emit albumSelected(albumId);
         });
     }
     if (artistId > 0) {
-        auto *openArtist = menu.addAction(tr("Go to artist: %1").arg(artistName));
+        auto *openArtist = menu.addAction(tr("Go to artist: %1").arg(QString(artistName).replace(QLatin1Char('&'), QStringLiteral("&&"))));
         connect(openArtist, &QAction::triggered, this, [this, artistId] {
             emit artistSelected(artistId);
         });
@@ -252,7 +252,7 @@ void SearchTab::onAlbumContextMenu(const QPoint &pos)
     const QString artistName = albumJson["artist"].toObject()["name"].toString();
     if (artistId > 0) {
         menu.addSeparator();
-        auto *openArtist = menu.addAction(tr("Go to artist: %1").arg(artistName));
+        auto *openArtist = menu.addAction(tr("Go to artist: %1").arg(QString(artistName).replace(QLatin1Char('&'), QStringLiteral("&&"))));
         connect(openArtist, &QAction::triggered, this, [this, artistId] {
             emit artistSelected(artistId);
         });